Blades of a rotary flow machine, such as a compressor unit or a turbine stage of a gas turbine arrangement, are typically circumferentially arranged on a plurality of axially ordered rotor wheels. The platforms of each blade delimit the working channel of the rotary flow machine, which in case of a turbine stage is the hot gas channel where hot gases emerging from an upstream combustor expand and convert kinetic energy into rotational mechanical energy. Highly-compressed air is typically extracted from the compressor unit of an axial turbine for the purpose of cooling turbine components, particularly those in the hot gas path downstream of the combustor. The cooling air is required to maintain the temperature of the turbine components at an acceptable level for operation, but comes at a cost to overall turbine efficiency and output. Therefore it is important to reduce any cooling flow leakage out of the turbine components.
The area between adjacent blades in a common blade row of a rotor wheel radially inward of the platforms of each blade is typically referred to as a shank pocket. Typically, cavities between rotating blades and axially adjacent stationary components axially forward and aft of each shank pocket operate at different pressures to enable a natural fluid flow from the higher pressure cavity to the lower pressure cavity through the gaps which are necessary for movement and expansion between adjacent rotating blades. Each of these gaps has a large leakage path for cooling flow to escape from the shank region of the blade. The cooling efficiency can also be impaired by ingress of hot gas from the hot gas path into the shank region.
Document EP 2 584 151 A2 discloses a sealing system for a turbine rotor blade having at least one shank pocket encircled radially outwardly by an axially extending portion of the platform. At least one radially directed rim extending from the trailing edge side of the shank has a radially orientated first slot for receiving a seal. The seal may be a strip seal comprising an arm portion and a hook portion wherein the arm and hook portions are shaped to mate with the slot such that the slot restrains the movement of the seal, wherein size of the seal substantially prevents a cooling flow from leaking through the shank pocket. Further, it is disclosed that the strip like seal bordering the shank portion of a first and a second blade that has a width that substantially prevents a cooling flow from leaking through the shank pocket.
A further sealing arrangement for a turbine blade is disclosed in the document US 2012/0237352 A. The sealing arrangement comprises two circumferentially adjacent arranged blades on a rotor wheel having an enclosed essentially radially oriented groove. The groove has at least one radial seal pin having an essentially uniformly round cross-section.